Knot tightening tool



FIG. 1 is a front elevational view of a knot tightening tool showing my new design;

FIG. 2 is a right elevational view thereof;

FIG. 3 is a bottom plan view thereof; and,

FIG. 4 is a top plan view thereof showing my design. 

The ornamental design for a knot tightening tool, as shown and described. 